Auckland's rapid reduction in movement during the first week of New Zealand's COVID-19 lockdown has been detected on the Auckland Volcano Seismic Network, GeoNet says.
The city's seismic noise is now at levels usually seen on a Sunday, GeoNet said in a statement on Thursday.
GeoNet operates a network of 11 seismometers in and around Auckland City as part of their National Volcano Monitoring System, designed to detect early signs of volcanic unrest in the city's volcanic field.
As cities create their own seismic noise, predominantly from vehicles, it can make identifying small earthquakes in the area quite difficult as it masks the shaking. To compensate, GeoNet places its sensors up to 380m below the surface to mask the majority of the noise generated by the city.
The organisation uses a technique called Real-time Seismic Amplitude Measurement (RSAM) to analyse noise developed by volcanic unrest.
"RSAM is a really valuable tool and is an excellent way of showing changes with time. For example, we can also see interesting trends from the outputs of noisy sites, like those near a city or coast," GNS Science volcanologist Brad Scott said in a statement.
"It allows us to see the daily commuting cycle around the city, the decrease of noise on the weekends and even the size of the sea swells from the Tasman Sea.
"As the country started #StayHomeNZ to help eliminate the spread of COVID-19, we recorded a significant decrease in noise about Auckland City by our seismometers."
As expected, the normal weekly cycle of the city's noise levels shows that Monday to Friday is the busiest period, before slowing down on Saturday afternoon and being the quietest on Sunday.
"Last week we could see the city start to slow down on Tuesday and Wednesday when New Zealand went to COVID-19 Alert Level 4. It has been at typical weekend levels since then," Scott explained.
"It’s great to see people staying at home as this is the best thing we can all do to stop the spread of COVID-19."
Thursday marks New Zealand's eighth full day in lockdown since Alert Level 4 was implemented. All schools and non-essential businesses have been closed nationwide and New Zealanders are required to remain at home in a bid to eliminate the virus.
As of Thursday, there have been 797 confirmed and probable cases of COVID-19 in New Zealand.
